Elliptical polarization electromagnetic energy radiation system



C. E. SMITH ELLIPTICAL POLARIZATION ELECTROMAGNETIC ENERGY RADIATIONSYSTEM Dec. 5, ,1950

5 sheets-sheet 1 Filed Nov. 14, 1946' TRANSM/ TTER Dec. 5, 1950 c. E.SMITH 2,532,428

ELLIPTICAL POLARIZATION ELECTROMAGNETIC ENERGY RADIATION SYSTEM FiledNOV. 14, 1946 5 Sheets-Sheet 2 Dec. 5, 1950 c. E. SMITH 2,532,428

ELLIPTICAL POLARIZATION ELECTROMAGNETIC ENERGY RADIATION SYSTEM 5Sheets-Sheet 3 Filed Nov. 14, 1946 HVVENTUR.

Dec. 5, 1950 c. E. SMITH 2,532,428

ELLIPTICAL POLARIZATION ELECTROMAGNETIC ENERGY RADIATION SYSTEM FiledNov. 14, 1946 5 Sheets-Sheet 4 INVENTOR. QM i.

C. E. SMITH ELLIPTICAL POLARIZATION ELECTROMAGNETIC ENERGY RADIATIONSYSTEM Dec. 5, 1950 Filed Nov. 14, 1946 5 Sheets-Sheet 5 Vertical DIfd/Q aQi Qw cosesln wi cos/6am w! Il /gag l8 *Jf c059 oswf E R/E cosGcas wt E cos 6 sm wt cos 9 cos w i E- +J cos Qposwf c039 claw! Ecases/rm; f

I N VEN TOR.

BY M W W Patented Dec. 5, 195i) ELLIPTICAL POLARIZATION ELECTROMAG-NETIC ENERGY RADIATION SYSTEM Carl E. Smith, Cleveland, Ohio, assignorof onehalf to United Broadcasting Company, a corporation of OhioApplication November 14, 1946, Serial No. 709,737

12 Claims. 7 1

My invention relates ingeneral to polarization'of radiated waves, andmore particularly to the limiting cases of circular and planepolarization of the general case of elliptical polarization of radiatedelectromagnetic waves.

The term circular polarization as used in this description, means thelimiting case of elliptical polarization of the electromagnetic field ina plane at right angles to the direction of propagation. In this planethe electric vector is of constant amplitude and rotates at the carrierfrequency in a clockwise or counter-clockwise direction.

The term plane polarization asv used in this description, means theother limiting case of elliptical polarization of the electromagneticfield wherein the wave energy is polarized in a plane parallel to thedirection of propagation. In this case the electric vector is'of varyingamplitude and does not rotate as in the case of circular polarization.

The term electromagnetic field is understood to contain an electricfield and a magnetic field in planes which are at right angles and theenergy therein contained is constant and continuously changes from oneform to the other. For the purpose of the following descriptionandclaims the term wave polarization? will refer onlyto the electricfield.

An object of my invention is to provide a method of transmittingradiated energy wherein a maximum number of receivers within a givenservice area will receive the radiated energy at least at a givenminimum signal level regardless of the orientation of a single straightdipole receiving antenna in a plane perpendicular to the line ofpropagation of the radiated wave energy.

Another object of my invention is the provision of a radiation systemfor establishing elliptical polarization, with circular and planepolarization as the two limiting cases, at least at the marginal area ornear the boundary of a given area which surrounds the radiator means.

Another object of my invention is the provision of a radiation systemfor establishing substantially non-directional elliptical polarization,with substantially non-directional circular and plane polarization asthe two limiting cases.

Another object of my invention is a radio system comprising two or moreradio transmitters and at least a radio receiver wherein means areprovided at the radio receiver for discriminating between clockwise orcounter-clockwise rotational directions of the circularly polarizedenergy Waves of the two or more radio transmitters,

invention may be had by referring to the following description andclaims, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a plan view of a radiating antenna that produceselliptically polarized waves;

Figure 2 is a sectional side view of the antenna taken on the line 2-2of the Figure 1;

Figure -3 shows the performance patterns of the field intensity at givenpoints within a specified service area for circular polarization;

Figure 4 diagrammatically shows in perspective two radio receiving setspositioned within the overlapping service areas of two radiotransmitting stations;

Figure 5 is a diagrammatic plan view of a receiving antenna designed toreceive or transmit elliptically polarized waves;

Figure 6 is a diagrammatic side elevation of the'receiving antenna shownin Figure 5;

Figure 7 is a diagrammatic plan view of another type of receivingantenna, designed "for use with elliptically polarized waves;

Figure 8 is a diagrammatic side elevation of the antenna shown in Figure'7;

Figure 9 is a diagrammatic perspective view of another type of receivingantenna designed to receive elliptically polarized waves;

Figure 10 is a diagrammatic side elevation of the antenna shown inFigure 9;

Figure 11 is a diagrammatic perspective view of still another type ofantenna designed to receive elliptically polarized waves;

Figure 12 is a diagrammatic side elevation of the antenna shown inFigure 11;

Figure 13 is a perspective view of an antenna system designed to producenon-directional diagonal plane polarized energy waves;

Figure 14 is a diagrammatic perspective view of a type of antennadesigned for use with diagonal plane polarized waves;

Figure 15 is a diagrammatic side elevation of the antenna shown inFigure 14; and

Figure 16 shows the performance patterns of the field intensity fornon-directional elliptical polarization;

Figure 17 is a sketch showing vector fields produced by an antennaproducing an elliptically polarized field intensity as governed byEquation 2;

Figure 18 is a sketch showing a circularly polarized vector E whichrotates clockwise of a sp cial two-element antenna which is governed byEquation 3.;

Figure 19 is a sketch showing a circularly plarized vector E whichrotates counter-clockwise of the special two-element antenna as governedby Equation 4;

Figure 20 is a sketch showing a. 45 degree polarized vector E asgoverned by Equation Figure 21 is a sketch showing a -45 degreepclarizedvector E as governed by Equation 6;

Figure 22 is a sketch showing an elliptically polarized vector E withthe major axis vertical;

Figure 23 is a sketch showing an elliptically polarized vector E withthe major axis horizontal; and

Figure 24 is a sketch showing a three-element circularly polarizedantenna as governed by Equation 7.

Generally my invention relates to methods of radiating electromagneticenergy, with particular emphasis on the methods and a system forimproving the reception of radio waves by a radio receiving set. In manyinstances, service areas or boundaries for certain radio transmittertypes and frequencies have been established, for instance, in the UnitedStates by the Federal Communications Commission, and my invention hasparticular reference to improving the reception of the transmitted waveenergy within these service areas. My invention materially increases thepossibility that a receiving antenra located at random in space willprovide satisfactory receptions.

To achieve the end of increasing the possibility of satisfactoryreception. with a randomly placed receiving antenna, my inventionprovides for the transmission of a circularly polarized wave energy,which is a specialized case of elliptical polarization. In actualpractice, circular polarization is difficult to attain, due to manyvarying and unpredictable factors; however, by

. correct design, circular polarization may be attained as closely asdesired.

With reference to the drawing, Figures 1 and 2 depict a simple type oftransmitting antenna which is designed to produce circular polarizationof the radiated waves. In Figures 1 and 2, the reference character l8generally represents a vertical antenna Or radiator means and I9generally represents a horizontal antenna or radiator means. Thevertical antenna I8 is a common half-wave center-fed dipole, or coaxialantenna, and the horizontal antenna I9 is a dipole loop, which iscircular in a horizontal plane, as shown in Figure 1. A transmitter 20supplies energy to both the horizontal and vertical antennas through thetransmission lines I4 and I5 respectively, which in the drawing areshown as coaxial cables. A junction box IS in the transmission line isused to couple both the vertical and horizontal antennas to thetransmitter 20. A tuning stub I1 is provided at the junction box toprovide a tuning arrangement in the transmission line to match theimpedance of the transmission line to the impedance of the transmitter20, and other ti'ning stubs may be placed in thetransmission 1i les l4and I5 if desired. The transmission line I that feeds the verticalantenna L8 is made onequarter wave length longer than the transmissionline l5 that feeds the horizontal antenna 19, in order to provide a 90degree difference of electrical phase between the two antennas l8 andI9. The vertical dipole l8 has a theoretically circular horizontalpattern of field intensity or energy level, and the horizontal antennal9, being a dipole loop, also has a theoretically circular horizontalpattern of field intensity or energy level. The two antennas l8 and I9are axially aligned to prevent distortion of the respective fieldintensity patterns by the other antenna. The effect of these twocircular horizontal patterns from these two antennas l8 and I9 is totend to cause equal radiation of the horizontally and verticallypolarized energy waves or field intensity in all horizontal directions;therefore the antenna as shown is non-directional in a horizontal plane.The degree electrical phase difierence between the two antennas l8 andI9 causes a rotating electrical vector which rotates in free space atthe carrier frequency as it is propagated; that is, one revolution ofthe electric vector for each wave length traversed along the line ofpropagation. This transmitting antenna will transmit circularlypolarized waves, if each antenna is fed with an equal amount of energy.Positioning a transmitter with an antenna of this type near the centerof a substantially circular service area would enable substantiallycircular polarization of the energy waves to be established fairlyeasily throughout the service area.

A single straight dipole half wave receiving antenna may efliciently beutilized to receive these circularly polarized waves and a novel featureof my invention resides in the fact that this receiving antenna may bepesitioned at random in a plane perpendicular to the line of propagationand .vet re eive a substantially constant voltage. Referring to Figure3, I show performance patterns of an antenna system such as is shown inFigures 1 and 2 for radiating circuarly polarized energy waves. In thecenter of Figure 3, I show the horizontal plane pattern 5| of thevertically and horizontally po arized waves. Ths horizontal planepattern has been oriented with north at the top of the page and showstwo substantially circular patterns, a. first pattern 56 which is asolid line for the horizontal polarization field intensity, and asecond'pattern 51 which is a dotted l ne for the vertical po'arizationfield intensity. I have shown two dash-dot circles in the Figure 3. Theouter dash-dot circle 52 is to depict the boundary or marginal area of agiven service area, such as for instance, a service area as allocated bythe Federal Communications Commission, as that area with n which a givenradio transmission station has been authorized to serve at a givenfrequency and at a given minimum si' nal level .of field intensity. Thesmaller dot-dash circle 53 is meant to represent an arbitrary boundarywith n the given service area also surrounding but nearer the radiotransmitter station. A first set 54 of eight polarization patterns 63 to10, inclusive, is shown just outside the first small dot-dash circe, anda second set 55 of eight more polarization patterns 1| to 18 inclusive,is shown just inside the large outer dot-dash circle. These patterns 63to la inclusive, give the relative field intensity in the horizontalplane of a straight dipole receiving antenna for all polarizations in avertical plane normal to the drection of propagation at points 3 tc 53inclusive, on the two circles 52 and 53.

The points 83 to 98 are numbered twenty numbers higher than thecorresponding patterns 63 to 18, inclusive, for that point. Thehorizontal plane pattern in the center of Figure 3 shows that thevertical antenna means has been energized at a relatively higher energylevel than the horizontal antenna means. A feature of my inventionpertains to methods for causing the field intensity patterns in themarginal area or near the boundary 52 of the given service area to berelatively circular, as depicted by the second set of patterns 55 nearthe large dash-dot circle 52. These patterns, II to 18 inclusive, forthe relative field intensity, have been shown as roughly circular.Figure 3 illustrates that it may often 'be' necessary to energize thehorizontal and vertical antenna means of the transmission station atdifferent energy levels, because of diiferent attenuation factors orother varying factors in these two types of polarized waves, so that afairly circular field intensity pattern will be established in themarginal area. of the given service area. In many cases, the attenuationfactor of each of the horizontal and vertically polarized energy wavesmight be substantially the same, in which case the vertical andhorizontal radiator or antenna means would be energized at approximatelythe same energy level, maintaining a substantially circular fieldintensity pattern throughout the entire service area.

It is a feature of my invention that the field intensity polarizationpatterns shall be as circular as possible in the marginal area of theservice area, as shown by the set of patterns 55 in Figure 3. In manycases the attenuation factors or degree of reflection or other varyingfactors may be different for the horizontal and vertical waves, and itmay be necessary to energize one antenna means at a higher energy levelthan the other. With this condition, locations closer to the transmitterstation than the marg nal area or boundary will have a higher fieldintensity, as shown by the larger area of the polarization patterns 54.With unequal energization of the two antenna means, these polarizationpatterns 54 will tend to become elliptical, because the field intensityin e ther the vertical or horizontal plane will be amplified more thanthe other, to become the major and minor axes of the ellipse. The minoraxis of the elipse of the patterns 54 will still be considerably greaterthan the diameter of the roughly circular polarization patterns 55, andif a straight dipole rece ving antenna is aligned with the minor axis ofthe ellipse of the patterns 54, the signal strength received will stillbe considerably above that minimum signal strength required for goodreception. When the attenuation factor and other variables for each ofthe vertically and horizontaly polarized waves are equal, theenergization of each antenna will be equal, or 50 per cent of thetransmitter power to each antenna. Where the variable factors cause adifference in the field intensity, different amounts of energy would beapplied to each antenna means to cause a difierence in the fieldintensities at and near the transmitter, which produces a circularpolarization of the field intensity at the marginal area. I find thatthe limits of variations in the field intensity need not exceed 30 percent to 70 per cent; that is, each antenna need be energized to producea field intensity of a minimum of 30 per cent, or a maximum of 70 percent, with the other antenna being supplied with the remainingtransmitter power. This limit of variations has been found to besufflcient to cause circular polarization at the marginal area with evengreat unbalance of the variable factors. The ratio of the fieldintensity produced by each antenna will therefore be a function of theattenuation factor of the wave energy in that plane of polarization.

Another novel feature of my invention provides for means for selectingbetween two or more transmitters that have overlapping or adiacentservice areas as illustrated in Figure 4, by providing means at thereceiving station which is within the overlapping portions of theseareas or near the boundary between adjacent areas, for discriminatingbetween one or the other at will. To provide for this, I employ areceiving antenna that will receive a circularly polarized wave, and byproper phasing, circularly polarized waves of either clockwise orcounter-clockwise rotational direction may be received, while the otheris rejected or eliminated.

In Figure 4, I illustrate diagrammatically first and second radiotransmitter stations 40 and 4! which have antenna systems 42 and 43,respectively. A first dot-dash circle GI depicts the boundary ormarginal area of the given service area of the first radio transmitter40, and a second dot-dash circle 62 similarly depicts the marginal areaof the second radio transmitter 4|. A first and a second radio receivingset 26 and 32 each having a different type of antenna system have beenshown within the overlapping portions of the two service areas, toillustrate two forms of antenna systems to discriminate betweencircularly polarized waves radiated from the two radio transmitterstations 40 and 4|. The method of operation of these two types ofantenna systems, and other antenna systems designed to receivecircularly polarized wave energy, will more readily be understood byreferring to the Figures 5 to 12. The antenna shown in perspective viewin conjunction with the radio receiving set 26 in Figure 4 is the sameas that shown in Figures 5 and 6, and the antenna shown in perspectiveview in conjunction with the radio receiving set 32 in Figure 4 is thesame as that shown in Figures '7 and 8.

Figure 5 is a top or plan view, the Figure 6 is a side view of one typeof antenna that will receive circularly polarized energy waves. Therepresentations of this antenna as shown in Figures 5 and 6 are merelypictorial sketches, and the physical support elements are not shown. Thereference characters 23 and 24 denote the transmission lines or coaxialcables that feed the vertical and horizontal half-wave dipoles 2| and22, repectively, and 25 is the common transmission line to the radioreceiving set 26. The length of the transmission lines 23 and 24 areeach oneeighth wave length long, therefore placing the two antennas 2iand 22 a quarter wave length apart in a horizontal plane. This antennamust be properly oriented as to direction to the transmitting station,with the line formed by the transmission lines 23 and 24 pointing towardthe transmitting station. This is necessary so that there is one-quarterwave length difference in distance to the transmitter station from thehorizontal and vertical antennas and a ninetydegree phase difference isproduced in the two antennas thereby. This ninety degree difference inelectrical phase between the horizontal and the vertical receivingantennas and an equal length of transmission line into the radioreceiving set will enable this antenna system to receive circularlypolarized energy waves. This antenna system will receive circularlypolarized energy waves from either of two directions, that is, forinstance in Figure 4, from either the transmitter 40 or 4|. However,dependence is made upon the manner of phasing the two antennas 2| and 22in order to determine whether clockwise or counterclockwise rotationaldirection of the circularly polarized waves will be received orrejected. For purposes of illustration, let us assume the transmitterstation 40 is transmitting circularly polarized waves which are rotatingclockwise as viewed by an observer looking away from the transmitterstation 40. This clockwise rotational maximum vector is intercepted bythe vertical receiving antenna 2|, and at the same instant of time amaximum field intensity vector will be W received by the horizontalreceiving antenna 22.

If the connections are such that the voltage received by the twoantennas 2| and 22 are additive, then twice the signal strength receivedby one antenna alone is supplied to the radio receiving set 28. If theconnections are so made that the signal voltages received by the twoantennas oppose each other, theoretically there will be no signalsupplied to the radio receiving set 26. With such a connection,clockwise rotating waves would be rejected and counter-clockwiserotating waves would be accepted. It will be noted that if the entireantenna assembly is rotated 180 degrees in a horizontal plane, so thatthe horizontal receiving antenna 22 is closer to the transmitter stationthan the vertical receiving antenna 2|, there will be no diflerence asto the type of rotational wave energy that is accepted or rejected.

Figure 7 is a plan view and Figure 8 is a side view of another type ofreceiving antenna designed to receive circularly polarized waves, andthe theory of its design is quite similar to the theory of the design ofthe antenna shown in Figures 5 and 6. The antenna as shown in Figures 7and 8 has a vertical receiving antenna 21 and a horizontal receivingantenna 28. The vertical receiving antenna 21 is connected to a lengthof transmission line 29, and the horizontal receiving antenna 28 isconnected to a length of transmission line 30. A common transmissionline 3! joins the two transmission lines 29 and 30 to the radioreceiving set 32. In this antenna system, the two receiving antennas 21and 28 are equidistant from the transmitter station,

inasmuch as they are in the same plane. However, the transmission line29 is made a quarter wave length longer than the transmission line 30and therefore circularly polarized waves may be received on this antennasystem as well. For purposes of illustration, we shall assume a similarsituation as was assumed for the antenna system of the Figures 5 and 6,wherein the transmitter 40 is transmitting a circularly polarized wavehaving a clockwise rotational direction as viewed by an observer lookingaway from the transmitter station. With proper connections of thehorizontal and vertical receiving antennas to the transmission line 9|,clockwise or counter-clockwise rotational direction of wave energy maybe selected. With this particular type of antenna system, a rotation ofthe antenna system 180 degrees in the horizontal plane does make adifference in the receiving characteristics, in that if it was formerlyreceiving clockwise rotating waves, it will now reject these waves andreceive counter-clockwise rotating waves from that particular direction.

It is intended as fully within the scope of my invention in thedisclosure that the two dipole receiving antennas need not be in avertical and a horizontal plane, respectively, but may be positioned atany other angle in space as long as the two bear a ninety'degreephysical relationship to each other. It is also to be understood thatthe antennas may be at some other physical angle than ninety degrees,such as for instance, at 45 degrees if the difference in length of thetransmission line or difference in length of the line of propagation tothe radio transmitter is correspondingly changed, that is, to aneighthwave length difference rather than a quarter wave lengthdifierence.

Figure 9 depicts a perspective view and Figure 10 a side elevation ofstill another type 01' antenna, in which 26 again denotes a radioreceiving set, 46 is a dipole at a 45 degree angle to the horizontal,and 41 is a horizontal dipole. A common transmission line 50 joins theradio receiver 26 to two short transmission lines 48 and 49. The shorttransmission line 48 joins the 45 degree angle dipole 46 to the commontransmission line 50, and the short transmission line 49 joins thehorizontal dipole 41 to the common transmission line 50. Both the shorttransmission lines 48 and 49 are each a sixteenth wave length long,thereby spacing the two dipoles 46 and 41 an eighth wave length apart inspace. Upon proper phase connections and orientation in the direction ofthe transmitting station, the antenna system will receive circularlypolarized wave energy, because the length of the transmission lines areequal, and the electric vector of the radiated wave will have rotated 45degrees in space after being intercepted at its maximum value by thedipole 46, to be again intercepted by the dipole 41 also at its maximumvalue. The antenna system illustrated in Figures 9 and 10 is similar indirectional and phase characteristics to the antenna shown in Figures 5and 6, inasmuch as it will receive counter-clockwise rotating waves fromeither of two orientations, and requires a change of phase connection toreceive clockwise rotating waves from either direction of orientation.

Figures 11 and 12 show another type of antenna system designed to beresponsive to circular polarization, and has three dipoles in a verticalplane each bearing a 120 degree relationship to any other. A verticalantenna 33 is connected by a transmission line 34 to a radio receiver59. A first oblique antenna 35 is connected by a transmission line 36 tothe radio receiver 59. A second oblique antenna 31 is connected by atransmission line 38 to the radio receiver 59. The three antennas 33, 35and 3! are then connected 120 degrees apart in electrical phase to beresponsive to a circularly polarized field. This antenna system willhave a bi-directional characteristic. The receiver 59 must necessarilyhave input means designed to receive this energy, which is commonlydesignated as a three phase feeding or coupling system. This antenna canalso be 'used for bi-directional transmission of circularly polarizedwaves.

The antenna system illustrated in Figures 11 and 12 is similar to theantenna shown in Figures 7 and 8 in direction and phase characteristics,inasmuch as it will receive clockwise rotating waves from a radiotransmitter when properly oriented and connected in phase, andsimultaneously is capable of receiving counterclockwise rotating wavesfrom an oppositely positioned radio transmitter. A correct phaseconnection and a correct orientation in one direction only, not merelyin one of two opposite directions, is necessary to receive any givenrotational direction of circularly polarized waves from any given radiotransmitter.

The mode of operation of any of these types of antenna systems as shownin the Figures to 12 will now be more fully described as to theirapplication to the Figure 4. As hereinbefore described, the antennasystem used in conjunction with the radio receiver set 26, whencorrectly aligned and phased, will receive only clockwise rotationaldirection of energy waves and reject the counterclockwise rotatingwaves. This antenna system for the radio receiver 26 will receiveclockwise rotational direction of antenna waves from either of twodirections, that is, as shown in Figure 4 from either the transmitter ortransmitter 4|. To provide for discrimination between two types ofcircular polarization,

if the radio transmitter 40 is transmittingcircularly polarized energywaves having a clockwise rotational direction as previously described,and the radio transmitter at 4| is transmitting circularly polarizedenergy waves having a tional direction of energy waves from the radiotransmitter 4|, and receiving those energy waves of a clockiserotational direction from the transmitter 40. In another case, both thetransmitters 40 and 4| might be transmitting circularly polarized energywaves of the same rotational direction, for instance, a clockwiserotational direction. In this case, an antenna system as used with theradio receiver 32 would discriminate between the two. The theory ofoperation of this type of antenna has previously been described, and ithas been shown that with correct connection of the two antenna means 21and 28 to the transmission line, the alignment of the entire antennasystem is the deciding factor as to whether clockwise rotationaldirection of energy waves would be received from either the radiotransmitter 40 or 4|. To receive the wave energy from the radiotransmitter 40, the position of the antenna system of the radio receiver32 might be as shown in the drawing, and if so, to receive the waveenergy from the radio transmitter 4| and reject the wave energy from theradio transmitter 40, only the antenna system of the radio receiver 32need be rotated 180 degrees in the horizontal plane.

For either of the two antenna systems as shown in use with the radioreceivers 26 and 32 another method is possible for receiving wave energyof either rotational direction from either of the two radio transmitters4D or 4|, and that is to provide a switching means or connection meansof the transmission line so that the phase of the connection may bechanged, and as hereinbefore described this will change the type of therotational wave energy that is received.

Discrimination between clockwise and counterclockwise rotatingcircularly polarized waves isdifferent lengths of lead-in transmissionlines or different phase connections in the transmitter. The phaseconnections must be correct in either case, that is, the voltagereceived by each antenna must be additive. The underlyin principle isthat with any type of antenna system, the total length of the path ofthe propagated wave must compensate for the degrees difference inelectrical phase of the transmitted or radiated wave. For the type ofantenna system shown in the Figures 5 and 9. the phase difference iscompensated for in a quarter wave length or eighth wave lengthdifference in the length of the free-space distances from thetransmitter antenna to the vertical and horizontal dipoles. For the typeof antenna systems shown in Figures 7 and 11, the phase difference iscompensated for by the quarter wave length difierence in the length ofthe lead-in transmission lines or the coupling arrangement. Combinationsof these two types may also be effected, such as an eighth wave lengthdifference in free space between the two dipoles, and an additionaleighth wave length difference in the lengths of the lead-in transmissionlines. Other combinations are also feasible, such as might be obtainedby modifications of the antenna system shown in Figure 9, wherein thedipoles are only physically displaced 45 degrees, and have a separationin free space to correspond, that is, only an eighth wave length, ratherthan a quarter wave length. This antenna system could easily be modifiedto come under the second type of antenna systems illustrated in Figures7 and 11. This could be accomplished by placing the two dipoles in thesame plane normal to the line of propagation, and making an eighth wavelength difference in the length of the lead-in transmission lines. Ingeneral, all these various modifications have the same basis, acompensation for the phase difference between the waves radiated by thetwo antenna means of the transmitter.

While I have described in Figures 1 and 2 merely a simple form oftransmitter antenna that is designed to transmit or receive circularlypolarized wave energy, it is within the scope of my invention that otherforms of antenna means or radiator means may be employed to radiate ortransmit such circularly polarized energy waves. For instance, theantenna system shown in Figures 5 and 6 has been described as beingcapable of receiving circularly polarized energy waves in twodiametrically opposite directions. It is obvious that this antennasystem may therefore also be used for transmission oi circularlypolarized energy waves as well as the reception of these waves. Theantenna systems shown in Figures 7, 9 and 11 are likewise capable oftransmitting circularly polarized energy waves. The antenna systemsshown in the Figures 1 and 5 to 12 might be used at any other positionin space, for instance, these receiving antennas might be tilted 60degrees from their present position so that only a portion of the energywill be intercepted and yet at each position the receiving dipoles willstill bear the same relationship to each other.

Another feature of my invention is to provide substantiallynon-directional plane polarization, which in the prior art has beenimpossible with only one radiator means, with the exception of the planepolarized waves in either a horizontal or a vertical plane. An antennasystem to produce this diagonal plane polarization wave, as

it may be called, is shown in Figure 13. The antenna system shown inFigure 13 is a modification of the antenna system shown in Figures 1 and2, wherein I8 again represents a vertical antenna means, and I9represents a horizontal dipole loop. A transmitter 20 again feeds bothradiator means, the vertical antenna means l being fed throughtransmission line I4 from the junction box I6, andthe horizontal antennameans I0 is fed through a transmission line 00 from the junction box It.The significant difference between this antenna system and that shown inFigures 1 and 2, is that the length of thetransmission line 30 whichfeeds the horizontal dipole loop I9 is made equal to the length of thetransmission line I! that feeds the vertical antenna means I8. Thisachieves the result that both antenna means I8 and I9 are now in phase,and the resultant electric vector produced by the two antenna means willbe the vectorial sum of the two antenna means. As I have shown thesystem in Figure 13, the two radiator means would be fed with equalamounts of energy, and therefore the diagonal plane polarization wouldbe at a 45 degree angle. A novel feature of this system is that thisdiagonal plane polarization is non-directional in the horizontal plane.This antenna system will produce diagonal plane polarization that isnon-directional, that is, will have a constant angular position as seenby an observer regardless of position from the antenna system. The twoantenna means could easily be energized at other than equal magnitudes,in which case the diagonal plane of polarization would be other than 45degrees, but would still be the resultant vector sum of the two fieldintensity vectors. I

In Figures 14 and is shown a type of receiving antenna system that isdesigned to receive diagonal plane polarized waves. The antenna systemshown has an antenna means 44 connected by a transmission line 45 to aradio receiving set 26. The antenna means 44 is positioned at a 45degree angle with respect to the horizontal, and is slanted upwardly tothe left as viewed from the right hand side of the drawing. Thereception of diagonal plane polarized waves is dependent on the phaseconnection of the transmitting antenna means I8 and I9, and if the phaseconnection is such that the diagonal plane of'polarization is upward tothe left as viewed from the right side of the drawing, then thereceiving antenna system shown in Figure 14 will receive the. diagonallyplane polarized waves transmitted by the antenna system of Figure 13.

If the phase connections of the transmitting antenna system of theFigure 13 were reversed, then the antenna system shown in Figure 14would not receive this energy radiation, because the diagonal plane ofpolarization would be at right angles to that plane of polarizationwhich the antenna system of Figure 14 will accept. By rotating theantenna system shown in Figure 14 90 degrees in a vertical plane, or 180degrees in a horizontal plane, would again enable this receiving antennasystem to accept the radiated energy from the antenna system of Figure13.

The aforementioned description as to the phase connection importance inthe diagonal plane polarization of waves, is the basis for understandinganother novel feature of my invention wherein diagonally plane polarizedwaves of two or more transmitter stations may be selected or rejected bya receiving station located in or near the overlapping area of the givenservice areas of the respective transmitter stations. The explanationfor this selection or rejection would be quite similar to theexplanation already given for that of Figure 4. Selection between two ormore transmitter stations can be achieved by having an antenna systemsimilar to that shown in Figure 14, which is rotatable in a verticalplane or preferably in a horizontal plane, and then the transmittedwaves that are desirous of being received can be selected by properorientation of the receiving antenna system.

The antenna system shown in Figures 1 and 2 will produce non-directionalcircular polarization, and the antenna system shown in Figure 13 willproduce non-directional diagonal plane polarization, which are thelimiting cases of nondirectional elliptical polarization. In Figure 16,performance patterns of the general case of nondirectional ellipticalpolarization are shown. Performance patterns shown in Figure 16 arequite similar in general character to those performance patterns shownin Figure 3. In the center of Figure 16 is shown the horizontal planepattern I03 of the vertically and horizontally polarized waves. Thishorizontal plane pattern has been oriented with north at the top of thepage and shows two substantially circular patterns, a. first pattern IOIwhich depicts the horizontal polarization field intensity, and a secondpattern I02 which depicts the vertical polarization field intensity.Since I have chosen to show equal relative magnitudes of energization ofthe two antenna means, these two patterns of the horizontal andvertically polarized field intensity are coincident. A recurrent lineI04 depicts the boundary of a given service area. and a set of .eightpolarization patterns I05 give the relative field intensity pattern inthe horizontal plane of a straight dipole receiving antenna for allpolarizations in a. plane normal to the line of propagation atequi-spaced points on the boundary I04. The set of eight polarizationpatterns I05 are consecutively numbered from I I I to I I8. andrepresent the polarization patterns at the points III to I28 on theboundary I04. The polarization pattern for the given point is ten unitslower in number than the corresponding point on the boundary I04. Theset of eight polarization patterns I05 all show an elliptical patternwith the major axis sloping upwardly toward the right and therefore showthat the elliptically polarized wave is non-directional in a horizontalplane.

For a theoretical point source radiator of elliptically polarized wavesthe instantaneous vector field intensity in free space can be writtenwhere E=mv/m, the instantaneous total vector field intensity measured ata distance a in a plane at right angles to the direction of propagation,

Emk=mv/m, the maximum vector field intensity produced by the Itradiating element and measured at a. distance a. in a plane at rightangles to the direction of propagation,

It is' possible to use more than one point source radiator to produceelliptically polarized waves. In such cases it is feasible to use anumber of point source radiators, some contributing one component andsome another component, the sum of which at a point a in space will addvectorially to produce the desired elliptically polarized fleldintensity.

For the special case of a vertical dipole and a horizontal loop havingthe same center of gravity in space as shown in Figures 1, 2 and 1'7 wecan write the following equation for their instantaneously ellipticallypolarized field intensity in space,

where Emn=mv/m the maximum vector field intensity produced by thehorizontal loop antenna in the horizontal plane measured at a distance ain a plane at right angles to the direction of propagation,

fh (0,) =cos- 0, the vertical radiation characteristic of aninfinitesimal horizontal loop antenna. Since the pattern isnon-directional in the horizontal plane the variable does not appear inthe equation, 1

0=elevation angle from horizontal plane,

bn=time phase angle of the horizontal vector field intensity Ema, IE'mo=mv/m, the maximum vector field intensity produced by the verticaldipole in the horizontal plane measured at a distance a in a plane atright angles to the direction of propagation,

fv(0,) =cos 0, the vertical radiation characteristic of an infinitesimalvertical dipole antenna. Since the pattern is non-directional in thehorizontal plane the variable does not appear in the equation,

11Iv=time phase angle of the vertical vector field intensity Emv.

Figure 17 is a sketch showing vector fields produced by the special typeof elliptically polarized transmitting antenna of Equation 2,

In Equation 2 let lEm[=]Emh|=|Emvl, glib- 0 and lw=90 Making thesesubstitutions,

i=2". cos 0(sin ot+J 005 wt) (3) This is the equation of a circularlypolarized vector E which rotates clockwise, as shown in Figure 18, in aplane at right angles to the direction of propagation.

Now in Equation 2 let |amf=lzmhl=lzmt n=180 and os=9o Making thesesubstitutions,

E==Em cos 0(-sin wt+J cos wt) (4) This is the equation of a circularlypolarized vecelement. This effect could also have been accomplished byreversing the conenctions to the vertical dipole. If the connections toboth the horizontal and vertical elements are reversed the direction ofrotation will not be altered.

V In Equation 2 let lEml=lEmh|=lEmoL and lllh=v=90 With thesesubstitutions,

E=E'm cos 0 cos ot(1+J) (5) which is the equation of +45 degreepolarization as shown in Figure 20.

If in Equation 2 |Em|==IEmhI=|Emul, oh=27o one v= which if substitutedyields,

E=Em cos 0 cos wflJ-l) (c) which is the equation of 45 degreespolarization as shown in Figure 21.

Diagonal polarization results when the vectors Emh and Emv are in phaseor exactly out of phase giving respectively positive or negativediagonal polarization. 45 diagonal polarization is produced when|Emh|=]Ema|.

If |Emnl |Ems| in the case of diagonal polarization the angle ofpolarization as measured from the vertical can be varied from 0 to 45 asthe ratio of polarization as measured from the vertical can be variedfrom 45 to 90 as the ratio mil m varies from 1 to So far we haveconsidered the special case of circular polarization and all cases ofdiagonal polarization. These are all special cases of ellipticalpolarization.

If the phase between Emh and Emv is 90 but |Emh| |Emvl then ellipticalpolarization with major axis vertical and minor axis horizontal as shownin Figure 22 results. If |Emh| lEmu| then the major axis is horizontaland the minor axis is vertical as shown in Figure 23. These two cases ofelliptical polarization are for clockwise rotation because n=0 and1pv=90. If rim 1S reversed, that is, made 180, then counter-clockwiserotation will result.

Elliptical polarization with the major axis at any angle between 0 and90 can be produced by properly selecting the magnitudes of the vectorsEmh and Em and properly selecting the phase angles p11 and \I v.

In all of the above cases for the two element elliptically polarizedantenna the polarization and field intensity does not vary in thehorizontal plane.

Consider the following special application of Equation 1 for a threeelement circularly polarized antenna,

E=Em1 cos wt+Emz cos (wt+) +E'ma cos (wt-+240) (7) where Em, Em: and arevectors produced by a three phase antenna as shown in Figures 11, 12 and24. At various times in a cycle the following table gives the solutionof Equation 1 and shows that the field is circularly polarized androtates in a clockwise direction:

Elliptical polarization has been described as the general case, withplane polarization and cir-' ,ization planes must be fed in phase, thatis, in"

a zero phase relationship. To efiect circular polarization, the phaserelationship between the radiator means must be proportional to theangle between the planes of polarization. A formula may be used toexpress the phase relationship necessary between the radiator means.This for mula may be expressed as:

Electrical phase angle-21rniA where A is the dihedral angle between theplanes of polarization and is expressed in radians, and n is anypositive integer including 0.

To express the phase relationship in the general case of ellipticalpolarization, and to include the two limiting cases of circularpolarization and plane polarization, the relationship may be expressedas: the electrical phase relationship between said radiator means is afunction of a variable having limits 21miA and 0.

means for establishing first and second wave polarization planes, eachof said radiator means establishing substantially identical fields insaid first plane, means to energize said radiator means from saidcorrespondingly numbered output means, and means to energize saidradiator means in phase and at any relative magnitude of energization.

3. A radio system comprising at least a radio receiving set and firstand second radio transmitting sets, means for radiating from the firstand second radio transmitting sets first and second energy wavesnondirectional in the horizontal plane,,sald energy waves havingsubstantially equal components in the horizontal and vertical" planes inall directions in the horizontal plane, receptor means atsaid radioreceiving set capable of receiving said first and second energy waves,said energy waves at said radio receiving set having a difference inazimuthal direction or characteristic of polarization, and a combinationof The relative magnitudes of energization is critical in the case ofcircular polarization, where the radiator means must be energized at thesame relative magnitude. For either elliptical polarization or planepolarization, the magnitudes of energization may be of any relativevalue.

In the present specification and claims, the term "circular polarizationshall be defined to include true circles as well as ellipses in whichthe major axis thereof is not more than substantially 20 per centgreater length than the minor axis.

Although I have described my invention with a certain degree ofparticularity in its preferred form, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. A radiation system to effect plane polarization in at least a firstplane of an electromagnetic field created by radiating electromagneticenergy, said system comprising electromagnetic energy producing meanshavin at least first and second relatively variable output means, atleast first and second radiator means for establishing first and secondwave polarization planes, means to energize said radiator means fromsaid correspondingly numbered output means, and means to energize saidradiator means in phase and at any relative magnitude of energization.

2. A radiation system to effect substantially uniform plane polarizationin at least a first plane of an electromagnetic field created byradiating electromagnetic energy, said system comprising electromagneticenergy producing means havin at least first and second relativelyvariable output means, at least first and second radiator phaseconnecting and directional ,means at the said receptor means fordiscriminating between said first and second energy waves.

4. A radiation system including first and second electromagnetic wavesat least one of which is being radiated from a source substantiallynondirectional in the horizontal plane, said waves having substantiallyequal horizontal and vertical components in'all directions in thehorizontal plane, receiving means upon which both waves are adapted toimpinge, and a combination of spacing, phasing and directional controlmeans at said receiving means to-discriminate between a characteristicdifference in the azimuthal direction and polarization of said waves.

5. A radio system comprising, at least a radio receiver and a radiotransmitter, means for radiating from said transmitter radio energywaves which are substantially circularly polarized in all directions ofradiation in at leasta given plane 1 and which have a given rotationaldirection, receptor means at said receiver capable of receiving saidcircularly polarized energy waves of said given rotational direction,and means at said receptor means for selectively rejecting circularlypolarized waves of the opposite rotational direction.

6. A radio system comprising, at least a radio receiver and a radiotransmitter, means for radiating from said transmitter radio energywaves which in all directions of radiation are substantially diagonallyplane polarized with an attitude in at least a first plane at a givenacute angle to the first plane and which attitude remains substantiallyconstant in said first plane relative to radii from said transmitter,receptor means at said receiver capable of receiving said diagonallypolarized energy waves of said given acute angle of polarization, andmeans at said receptor means for selectively rejecting diagonallypolarized waves polarized in a plane perpendicular to said plane ofpolarization at said given acute angle.

7. A radio system comprising, at least a radio receiver and a radiotransmitter, means for radiating from said transmitter radio energywaves which in all directions of radiation are elliptically polarizedand which have a given rotational di rection and which ellipse remainssubstantially constant in shape and attitude of the major axis relativeto radii from said transmitter in at least a first plane, receptor meansat said receiver capable of receiving said elliptically polarized energywaves of said given rotational direction, shape and attitude, and meansat said receptor means 17 for selectively rejecting ellipticallypolarized energy waves having a difierence in one of said rotationaldirection, shape and attitude from said receivable ellipticallypolarized energy wave.

8. A radiation system to effect in at least a first plane anelectromagnetic field which in all directions of radiation isestablished by an elliptically polarized energy wave of a given shapeand attitude, said system comprising, electromagnetic energy producingmeans having at least first and second relatively variable output means,at least first and second radiator means having respectively first andsecond wave polarization planes, said first and second wave polarizationplanes having a given angle A therebetween, said radiator means adaptedto establish substantially identical fields in said first plane, meansto energize said radiator means from said correspondingly numberedoutput means, means to energize said first and second radiator means inphase relationship as a function or a variable having limits of 2miA and0, where A is expressed in radians and n is any positive integer, meansto energize said radiator means in equal magnitudes of energization andestablishing said variable at said first named limit of 21rn *-.A toeffect substantially circular polarization of the radiated wave in alldirections of radiation, means to energize said radiator means in anyrelative magnitude of energization and establishing said variable atsaid second named limit of zero to effect substantially planepolarization of the radiated waves in all directions of radiation whichwaves in at least said first plane have an attitude at a given acuteangle to the first plane and which attitude remains substantiallyconstant relative to radii from said radiator means, and means toenergize said radiator means at any relative magnitude of energizationand any value of the variable between the said limits to effectelliptical polariza-' tion of the radiated wave which in at least saidfirst plane has a given shape and attitude.

9. An antenna system for electromagnetic energy transducer means havingfirst and second connection means, said system comprising, first andsecond antenna means having respectively first and second wavepolarization planes, said first and second wave polarization planeshaving a given angle A therebetween other than zero, said antenna meanshaving substantially identical field patterns in at least a given plane,means to couple said first and second antenna means to said first andsecond connection means, respectively, in a phase relationship as afunction of a variable having limits of 21rniA and zero, where A isexpressed in radians and n is any positive integer, and means to couplesaid first and second antenna means to said first and second connectionmeans, respectively, with equal conductance and to establish saidvariable at said first named limit of 21mi-A to condition said antennameans for substantially circular polarization of the elec'- tromagneticenergy waves in said given plane in all directions from said antennameans,

10. An antenna system for electromagnetic energy transducer means havingfirst and second connection means, said system comprising, first andsecond antenna means having respectively first and second wavepolarization planes, said first and ncond wave polarization planeshaving 18 a given angle A therebetween other than zero. said antennameans having substantially identical field patterns in at least a givenplane, means to couple said first and second antenna means to said firstand second connection means, respectively, in a phase relationship as afunction of a variable having limits of zrniA and zero, where A isexpressed in radians and n is any positive integer, and means to couplesaid first and second antenna means to said first and second connectionmeans, respectively, with any relative value of conductance and toestablish said variable at said second named limit of zero to conditionsaid antenna means for substantially plane polarization of theelectromagnetic energy waves of a substantially constant attitude insaid given plane in all directions from said antenna means.

11. An antenna system for electromagnetic energy transducer means havingfirst and second connection means, said system comprising, first andsecond antenna means having respectively first and second wavepolarization planes, said first and second wave polarization planeshaving a given angle A therebetweenother than zero, said antenna meanshaving substantiall identical field patterns in at least a given plane,means to couple said first and second antenna means to said first andsecond connection means, respectively, in a phase relationship as afunction of a variable having limits of 21rniA and zero, where A isexpressed in radians and n is any positive integer, and'means to couplesaid first and second antenna means to said first and second'connectionmeans, respectively, with any relative value of conductance and anyvalue of the variable be tween said limits to condition said antennameans for substantially elliptical polarization of the electromagneticenergy waves of a substantially constant shape and attitude in saidgiven plane in all directions from said antenna means.

12. In an electromagnetic energy radiating sys tem, the method ofproducing substantially uniform plane polarization in at least a givenplane of the electromagnetic field created thereby, comprising,radiating a first electromagnetic wave in a first wave polarizationplane to create a first field pattern in at least said given plane,radiating a second electromagnetic wave in a second wave polarizationplane to create in at least said given plane a second field patternsubstantially identicalto said first field pattern, and establishingsaid radiations in an in-phase relationship.

CARL E. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

